During the Southern Song Dynasty, the Han River Basin was full of river pirates. In order to eliminate the banditry, the imperial court sent Zhang Gai, an elite member of the "Hengjiang Army", as a special envoy to investigate major cases on the river. During the investigation, he met a retired soldier named Mo Ke by chance, and the two of them established a friendship despite misunderstandings. It happened that the jade pendant of Mo Ke's relative was abducted by river pirates. The two worked together to rescue the jade pendant and the abducted child, and brought the river pirates to justice, restoring peace to the area.